Field of Invention
The present disclosure relates to a low-melting adhesive film including low-melting polyurethane as an adhesive layer. Since the low-melting adhesive film of the present invention exhibits excellent adhesive strength even at a low temperature when a sound absorbing material is adhered to a carpet fabric, it can be effectively used in interlay adhesion between the carpet fabric and a sound absorbing and proofing composite carpet to which a sound absorbing material is laminated.
Description of Related Art
Carpets or various sound absorbing and proofing materials have been widely used to reduce noise, vibration and harshness (NVH) of vehicles and improve vehicle interior environment.
Generally, carpets or various sound absorbing and proofing materials have a sound proofing structure made of fabrics having a variety of laminated structures, but recently, the research for the development of a sound absorbing and proofing composite material with sound absorbing properties has been intensively carried out.
In particular, the conventional carpet has a structure in which the lower part of the carpet fabric is made of a sound proofing material, and the lowest part thereof is treated with an AP (application processor) coating having a weight of 700˜1200 g/m2, wherein the AP coating is composed of polyethylene, elastomer, EVA and the like and includes an adhesive ingredient. The sound absorbing material, in which a polyethylene film is adhered to polyurethane foam, is then bonded to the carpet fabric. In this case, the polyethylene film is adhered to the AP coating by using adhesive strength of the AP coating rather than its own adhesive strength, to thereby manufacture a carpet with the sound absorbing material. Thus, during the conventional process of laminating the carpet fabric and sound absorbing material in the manufacture of a sound absorbing and proofing composite carpet, the carpet fabric is heated in an oven at a temperature of 180° C. or higher, the AP coating is melted due to the heating, the polyethylene film bonded to an expandable sound absorbing material is adhered to the melted AP coating layer, and then, the resulting carpet fabric is molded into a sound absorbing and proofing composite carpet through a cooling mold.
As described above, the conventional manufacturing process of a conventional sound absorbing and proofing composite carpet is complicated, and there is a need to improve durability and lightening thereof. In addition, demand for the application of a high strength material which is favorable to manufacture a sound absorbing and proofing composite carpet compared with the application of an AP coating has been increased.
On the other hand, in order to laminate polyurethane foam as a sound absorbing material to the carpet fabric, it is necessary to use an adhesive agent between them, and for this, the research for the development of an adhesive agent or an adhesive film should be accompanied.
As an adhesive film previously reported, Korean Patent No. 10-0842218 discloses a hot-melt thermoplastic polyurethane resin for an adhesive agent and a laminate film including the same, which is obtained by controlling melting points of a heat resistant thermoplastic polyurethane resin used as a protective layer for a laminate film and a hot-melt thermoplastic polyurethane resin used as an adhesive layer such that it has different melting points.
In particular, it discloses a laminate film which is characterized by manufacturing the following steps: forming an adhesive layer by using a hot-melt thermoplastic polyurethane resin which is obtained by reacting polyol (polyester diol, polyether diol) with a molecular weight of 1,500-2,500, a bifunctional chain extender and organic diisocyanate (aromatic, aliphatic, alicyclic isocyanate) and has a melting point of 80 to 140° C., forming a protective layer by using a heat resistant thermoplastic polyurethane resin which is obtained by reacting polyol (polyester diol, polyether diol), a bifunctional chain extender (butanediol) and organic diisocyanate (aromatic, aliphatic, alicyclic isocyanate) and has a melting point of 160° C. or higher and a softening point of 81° C. or higher, adhere the adhesive layer and protective layer to each other under pressure.
Also, Korean Patent Application Publication No. 2012-109062 discloses a hot-melt thermoplastic polyurethane resin for adhesion and an adhesive layer having excellent elongation, a hot-melt thermoplastic polyurethane resin for a protective layer having excellent elongation and heat resistance, and a film manufactured by using the same.
In addition, Japanese Patent Application Publication (Kokai) No. 9-221640 discloses a thermoplastic polyurethane resin having a flow initiating temperature ranging from 80 to 150° C. which is characterized by including one or more methyl side-chains within a molecule made of aliphatic diisocyanate, polyhydric diol and a chain extender, and a hot-melt film adhesive agent with excellent low temperature flexibility which is obtained by hot press forming the same. US Patent Application Publication No. 2011-112270 discloses a low-melting polyurethane elastomer obtained by reacting polyester polyol, methylene diphenyl diisocyanate (MDI), and a linear diol chain extender having 5 or 7 carbon atoms between hydroxyl (OH) groups of diols.
These adhesive films or adhesive agents used in the prior arts described above have a similar composition in the manufacture of a hot-melt thermoplastic polyurethane resin as an adhesive film and include isocyanate and diol as an adhesive polymer. However, there are problems in that they are apt to be separated due to their low adhesive strength, and their high adhesion temperature makes it difficult and complicated to manufacture them.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.